s14 transmission problems

[Nfire247]

Problem: When I put the car in Drive (or anything else) it doesn't move and free-rev's like its in neutral. When in neutral, the car rolls freely when pushed.

Back Ground:
I picked up a 1996 240sx with bad compression a few months ago. It has an automatic transmission.

I swapped the engine to an s13 Ka I found cheap locally and it cranks and runs fine now.
The problems are with the transmission.
Unfortunately this was the first time I'd installed an automatic transmission and I messed up. I destroyed the first transmission (original transmission from the s14) by not properly seating the torque converter before bolting up the trans to the block, it ended up pushing the input shaft from the transmission into the transmission... needless to say that trans didn't work.

I installed the auto trans that came with the S13 engine that I put in the car. I drilled a spot for the crank sensor in the bellhousing, and everything went together smoothly. I used the torque converter from the s13 engine/trans, and made sure to align it properly.
When the car was back together, I put fluid in the transmission and then tried driving it. The car didn't move at all, although the reverse lights come on when in reverse and Park kept the car from moving. The car didn't throw any CEL's when running.

I wasn't sure that trans. was good, so I bought another s14 trans. (it didn't come with a torque converter) and installed it yesterday. It went in without a hitch, I still used the s13 torque converter. After adding fluid, it acts exactly like trans. number two. Free revs when in gear. It is throwing a CEL now, but I haven't gotten a chance to check it yet, doubt its related (something probably worked its way loose) but still worth mentioning.

Anyone have any ideas?

[Nfire247]

Anybody? Could this be due to a bad torque converter? Its just hard to believe that two transmissions are bad in the exact same way.

[Nfire247]

How about this, does anyone know if in S14 240sx's the ecu has anything to do with the transmission going into Drive?
I think I've narrowed it down to either the torque converter or the ecu... if it has anything to do with it.

[biggie]

Did you remember to bolt on the flex plate to the transmission?

Doubt its the ECU (unless you've done some S13 electronics swaping).

[Nfire247]

Haha yeah, I bolted the torque converter to the flex plate... I would have been super happy if that was the answer though!

Nahh no wiring mess at all, it looks completely stock actually.

[Nfire247]

A new torque converter didn't help at all, same problems, I am very sick of this project.

Is there any sort of electronic control for the transmission?
Does the ecu do anything to the trans?

[compactfean]

There is a transmission control module that runs everything. Also shift silonoids can go out. Have you fallowed the procedure in the fsm for this problem?

[Nfire247]

Finally! you sound like you know what you're talking about. I need to do some research on the transmission control module.
The solenoids are located inside of the transmission right? So since I've had two transmissions doing the same thing I'm assuming for now that those aren't the problem.
Where is the procedure? I searched but I couldn't find anything that seemed relevant to this problem.

[compactfean]

Most solinoids are in the trans, under the trans filter.....although im not 100% on these transmissions because I ditched mine years ago...although I've done a ton of shift packs on Dodge transmissions that were under the filter. Ill try to find that procedure for you when I have a chance. It should be in the electrical. Diag selection in the back.

[Nfire247]

Thanks, I'd really appreciate it. I'm also having some trouble finding a whole lot of info on the transmission control module you mentioned, I've gathered that its located above the ecu, are the s13 and s14 ones different?

[compactfean]

im not sure if the trans ecu is different from s13 to s14 but yes its above the ecu...way up in there i actually still have my trans ecu in there until i remove my dash and wire tuck everything. have you had someone check to make sure the shift linkage is moving when you shift from each gear? could be a stripped linkage. im still looking for some test procedures on the tcu for you.

[compactfean]

ah hah!!!!!! http://www.nicoclub.com/FSM/240sx/1989-90/AUTO_TRA.pdf here you go man. looks like you have some reading to do now...lol. i read a little of it and i was right. there are 2 different auto transmissions that are completely computer controlled. you will have to check your id tag to diagnose correctly but its all there. check page 7 at the top....torque converter not locking up procedure you might be interested in. keap us posted and good luck.

[Nfire247]

nice! thanks man, yea the shift linkage is moving the lever on the trans, but I'll read up on this. Thanks!

[Nfire247]

Ok, so I read over that info, very good! But it seems to me like I'm having a more general problem than anything listed in that fsm. I have checked the transmission codes by doing the O/D button procedure, all ten lights blink quickly and with the same speed, so I'm not throwing a code form the transmission. Also the A/T check lamp isn't blinking, which i should be doing if there is a problem present.

I've tried two torque converters, I also checked to make sure the gearing inside of the converter turned one way and not the other, don't know how much that tells me though. My first instinct would be that its not the converter itself just because I've already swapped it.

I'm thinking my next step should just be to replace the ATCU, I should be able to get one locally really cheaply, and that will be one more thing that I can check off the list if it doesn't fix it. I just pulled out my ecu and I didn't see it right away, where exactly is it? Like at foot level, glovebox level, top of dash. Also is it in the middle, or closer to the engine side or door side? How big is this thing?

[compactfean]

Its almost the size of your ecu. Its way up there you'll have to remove glove box. Lay on your back with a flashlight and its bolted to the side just like the ecu. It did say that of there were any electrical " failures " than it would go onto safe mode and be in 3rd gear all the time..when you did the swap did you clean out the trans cooler? Maybe its clogged. Oh and if you can't find a tcu locally I can sell you mine. Your right, wouldn't hurt to replace it. I would see if its at least getting main power supply.

[Nfire247]

Hmm, no I didn't check the cooler, might be worth checking out.

Ok I'll take another look tomorrow, but I got in the floorboard with a flashlight and I didn't see it. I'll take the glove box out and see if that helps. Thanks, I'll let you know if I need yours, but I doubt it will be hard to find. Yeah I'll check the power wire too.

[Nfire247]

Found it! I was on the complete wrong side of the car haha. Its under the steering wheel, Close to where the clutch pedal would be if it was a manual

Now to find another one to throw in there!

[compactfean]

what ever it is you pulled is not it. its on the passenger side. trust me its up up up there. heres my proof ...second page. http://www.nicoclub.com/FSM/240sx/1989-90/ELECTRIC.pdf

[Nfire247]

hmm, well maybe because mine is an s14 its in a different place, I looked up the part number on it and its the Automatic Transmission Control Unit, looks a lot like an ecu, same kind of harness plug and everything. Weird

[compactfean]

Your chassis is a s13 correct.

[Nfire247]

No, the car I'm talking about right now is a 1996, sorry for the confusion

[compactfean]

Ah s***! Well when you do the diag on it make sure to use the procedure for your 96. Just Google 240sx fsm and the first one that pops up is all the fsms right here on Nico.it totally sounded like you found an s13 to drop a s14 motor in...plus your profile says 1990 so that's what I looked up. There shouldn't be to much difference in the fsms though.

[Nfire247]

haha yeah after your last post thats what I figured happened, its cool man, and all of the info you've given me it still relevant, and it helped me track down a good possibility of what my problem is. So thanks man, I'll post up if it fixes it or not.

[Nfire247]

Any idea if an ATCU from at 1997 will work in my 1996? the model number is different.

[compactfean]

It should still work because it runs the same trans. The only thing I would check is if the wiring pinout is different ....but I doubt it. You could also call a pickypart place and check there interchange.the only thing I can think of that would be different is maybe shift points.

[Nfire247]

thats what I was thinking too, good to hear. Keep ya posted!